Carburetor having adjustable precision fuel metering means



Dec. 13, 1966 R L. HAMMERSCHMIDT ETAL 3 ,2 ,46

CARBURETOR HAVING ADJUSTABLE PRECISION FUEL METERING MEANS 2 Sheets-Sheet 1 Filed Nov. 27, 1964 INVENTOR. RUDOLPH L. HAMMERSCHMIDT BY BILLIE R. SULLIVAN ATTORNEY Dec. 13, 1966 R. L. HAMMERSCHMIDT ETAL 3,

CARBURETOR HAVING ADJUSTABLE PRECISION FUEL METERING MEANS Filed Nov. 27, 1964 2 Sheets-Sheet 2 INVENTOR RUDOLPH L. HAMMERSCHMIDT BY BILLIE R. SULLIVAN mama. AQ

I49 ATTORNEY United States Patent 3,291,464 CARBURETOR HAVING ADEUSTABLE PRECHSEON FUEL METERING MEANS Rudolph L. fiiarnrnerschmidt, 912 Jeffery Drive, Pieasant Hill, Calif., and Billie R. Sullivan, 25 Poco Lane, Walnut Creek, Calif.

Filed Nov. 27, 1964, Ser. No. 414,099 14 Claims. (Cl. 261-142) The present invention relates to carburetors for internal combustion engines and more particularly to a carburetor for more precisely metering fuel into an engine under varied operation conditions.

A form of carburetor capable of superior performance is disclosed in US. Patent 2,236,595, entitled Carburetor, and issued to John Robert Fish, April 1, 1941. The mechanism, commonly known as the Fish carburetor, differs from conventional forms by delivering fuel into the venturi throat through apertures in the throttle plate shaft which extends thereacross. An optimum fuel and air mixture is obtained throughout a wide range of engine speeds inasmuch as the rate of fuel delivery is directly controlled by the angular position of the throttle.

In one variety of the Fish carburetor, this is accomplished by providing a radial arm on the throttle plate shaft that extends into the float chamber fuel volume. A passage extends through the arm from an opening in one sidethereof to the apertures in the throttle plate shaft to deliver fuel thereto. Adjacent the arm is a frat surface having a curved groove extending along the path which is travelled by the arm opening as the arm turns so that fuel is admitted into the opening through the groove. By making the groove of varying size along its length, the effective size of the fuel passage to the venturi throat is caused to vary as the throttle shaft is rotated. Thus through the use of suitable groove con figuration, the rate of fuel delivery is always accurately matched to the air intake of the carburetor.

In another form of the Fish carburetor the varying groove is carried on the moving arm while the fuel inlet opening is on the adjacent surface, the result being essentially similar to that described above.

The above described structure provides a more precise and continuous fuel metering control than conventional carburetors, resulting in greater fuel economy and improved engine performance. While the carburetor in its basic form is relatively prone to icing in cold humid weather, this problem is readily overcome by a de-icer of the type disclosed in US. Patent 3,128,321, entitled Carburetor De-Icer, issued to Hammerschmidt on April 7, 1964.

Although the Fish carburetor as heretofore designed has the advantages discussed above, the full potential for optimized fuel metering has not been realized under all operating conditions. In particular, the structure lacks adjustability with respect to the rate of fuel delivery at different throttle positions. The size of the fuel passage to the venturi for any throttle setting is fixed during manufacture by the configuration of the tapered groove. Once this has been done, there is no convenient means for making further adjustments to provide for varying operating conditions.

However, in order to truly optimize the mixture at all engine speeds, adjustments which cannot be anticipated at the factory may be needed. Using fuels of different octane rating, for example, may make such adjustment desirable. Similarly, such variables as air temperature, humidity, elevation or many others may affect the optimum size of the fuel passage for each throttle position. In addition, it is usually desirable that some means, preferably automatic, be provided for reducing the fuel passage slightly as the engine heats up. Further. the

special characteristics of particular engines may require some adjustment of the predetermined rate of fuel delivery for the various throttle positions.

The present invention is a Fish carburetor in which such adjustments may readily be made, the adjustable fuel delivery rate being provided for without sacrificing the basic simplicity which is an important advantage of such carburetors.

The difficulty in providin adjustability in a conventional Fish carburetor arises from the use of the tapered groove at one side of the pivotable radial arm. There is no practical means by which such a groove could be selectively restricted or expanded at selected portions of its length as would be required to make the desired adjustments. Accordingly, in the present invention the fuel passage opening is situated in the end of the radial arm rather than at the side thereof and a curved bar is disposed along the path travelled by the end of the arm, the bar being varyingly spaced therefrom to control the rate at which fuel can enter the arm. The bar is adjustably mounted on'a series of threaded supports, and is slightly flexible, so that its spacings from the end of the arm may be changed as desired at different points along its length.

The effective size of the fuel passage to the venturi is dependent upon the spacing of the bar from the opening in the end of the arm provided that the bar is close to the opening. Thus the passage may be reduced by bringing the bar, or a selected segment thereof, closer to the arm and the passage may be enlarged by withdrawing the bar slightly. This is easily accomplished by turning appropriate ones of the threaded supports which preferably extend through the wall of the fuel chamber and are therefore accessible from the outside.

The structure lends itself to various forms of automatic adjustment. For example, an element having a high coeflicient of thermal expansion may be disposed with one end fixed and the other bearing against a portion of the bar. As the engine heats up, the element expands slightly urging the bar towards the arm and thereby reducing the fuel passage slightly as is desirable under this condition.

Similarly, automatic means may readily be provided for enriching the fuel and air mixture while the carburetor is cold as in starting up.

By providing the more precise carburetion under varying operating conditions, the invention increases fuel economy, lessens maintenance costs and provides smoother engine performance. In addition the invention provides a further result which is of increasing importance in modern automobile usage. In particular the optimizing of the fuel and air mixture markedly reduces the irritating and hazardous components of engine exhaust such as carbon monoxide and the various hydrocarbons which are an important component of urban smog.

Accordingly it is an object of this invention to provide more precise control of the fuel and air mixture in an internal combustion engine.

It is an object of the invention to provide optimized carburetion under varying engine operating conditions.

It is another object of the invention to provide a Fish carburetor having provision for adjusting the rate of fuel delivery at different throttle settings.

It is still another object of the invention to provide a carburetor of the class in which fuel is transmitted to the venturi throat through the throttle shaft in which the size of the fuel passage for a given throttle position may be selectively varied.

It is a further object of the invention to provide a Fish carburetor with means for selectively adjusting the fuel and air mixture while preserving the basic simplicity of such carburetors.

Itis another object of the invention to provide a Fish carburetor having an automatic fuel passage adjustment for accommodating varying engine temperatures.

It is still another object of the invention to reduce undesirable engine exhaust gas components by more exact fuel carburetion.

The invention, including further objects and advantages thereof, will be better understood by reference to the following specification together with the accompanying drawing of which:

FIGURE 1 is an elevation view, in section, of a representative embodiment of the carburetor,

FIGURE 2 is a section view taken along line 22 of FIGURE 1 and showing details of the fuel metering structure of the carburetor,

FIGURE 3 is a section view taken along line 3-3 of FIGURE 2 showing a deceleration vacuum relief mechanism,

FIGURE 4 is a section view taken along line 4-4 of FIGURE 1 and showing the interior of the float chamber of the carburetor,

FIGURE 5 is a section view taken along line 5-5 of FIGURE 3 showing the internal construction of an acceleration pump disposed within the float chamber,

FIGURE 6 is a side elevation View of the carburetor showing fuel enriching means and associated mechanism, and

FIGURE 7 is a section view taken along line 7-7 of FIGURE 6 and showing further detail of the fuel enriching means.

Referring now to the drawing and more particularly to FIGURE 1 thereof, there is shown a Fish carburetor 11 of the type generally utilized on automotive engines, the invention being equally applicable to engines for marine, aircraft or stationary use. Carburetor 11 includes a body or barrel 12 having a cylindrical bore 13 therethrough which constitutes the venturi throat. An annular member 14 is secured to the top of barrel 11 to form a continuation thereof, the upper portion of member 14 having a bore 16 of greater diameter than throat 13. A sloping transition section 15 in the lower portion of 1nember 14 connects bores 13 and 16 to complete the venturi.

A flange 17 at the base of barrel 12 provides for mounting the carburetor on the intake manifold of an internal combustion engine and a shelf 18 is formed around the upper barrel member 14 to receive an air cleaner in the conventional manner. In order to forestall the icing difficulty to which this variety of carburetor is prone, an annular electrical heating element 19 is disposed between barrel 12 and member 14 in a recess 21 in the base of the latter, the structure and operation of the de-icer being more fully described in the hereinbefore identified US. Patent 3,128,321.

Considering now the mechanism for controlling the flow of air and fuel into the engine, a throttle shaft 22 extends transversely across the barrel 12, the shaft being journalled in the sidewalls thereof by bushings 23. Within the bore 13, a circular throttle plate 24 is secured to shaft 22 by clamps 26 so that by rotating the shaft the effective size of the air passage through the carburetor may be varied.

At one side of barrel 12, a radial crank arm 27 is secured to throttle shaft 22 and standard accelerator linkage 28 connects therewith for controlling the setting of the throttle. A coil spring 29 has opposite ends engaged with shaft 22 and barrel 12 respectively to urge the throttle towards the closed position. T 0 determine the idling speed of the associated engine, a second crank arm 31 is secured to shaft 22 and carries an adjustable screw 32 which seats against a stop 33 to selectively limit the degree of closing of the throttle.

At the opposite side of the barrel 12, a rectangular housing 34 for fuel metering elements is formed as an integral portion of the barrel and a wider rectangular float housing 36 is secured thereto, by bolts 37, with a gasket 38 being disposed between the two housings. Housings 34 and 36 are open to each other and thus form a single fuel chamber 39. In order to provide a convenient means for checking the fuel level within the float housing 36, a portion 41 of the other wall thereof is formed of glass or other transparent material.

Referring now to FIGURE 2 in conjunction with FIGURE 1, the fuel metering elements within housing 34 include a fuel pick-up arm 42 having an annular collar 43 formed at the upper end which fits on the end of throttle shaft 22 and is secured thereto. The arm 42, which extends downwardly into the fuel volume 44, thus pivots when'the throttle shaft 22 is rotated.

A fuel passage 46 extends longitudinally through pick-up arm 42 to connect an opening 47 at the lower end thereof with an axial passage 48 in the throttle shaft 22. As shown in FIGURE 1 in particular, the throttle shaft passage 43 extends to a series of spray apertures 49 spaced along the upper and lower surfaces of the shaft in the region of the throttle plate 26.

A tube 51 extends through the wall of barrel 12 to connect the upper region of housing 34 with the broad bore 16 at the top of the venturi. Accordingly, the pressure within housing 34 during operation is higher than that in the region of the spray apertures 49 which are in the constricted portion 13 of the venturi. Fuel is therefore drawn from the housing 34 through passages 46 and 48 and emitted from apertures 49 to mix with the air flow through the carburetor.

The rate of fuel delivery to barrel 12 by the above described means is dependent on the pressure differential between bores 16 and 13 which is in turn a function of the rate of air flow through the carburetor. Thus the fuel delivery rate is to some extent self regulating as it increases and decreases in accordance with the air demand by the associated engine. However in the absence of further control, this will not provide a satisfactory mixture ratio for all operating speeds.

The rate of fuel delivery is also dependent on the effective size of the fuel passage between the housing 34 and bore 13. According more satisfactory mixture control is effected by arranging for a variation in this parameter to accompany a variation in the throttle setting. This generally requires arranging for a progressively enlarging fuel passage as the throttle is moved from the closed to the open position.

The mechanisms theretofore used for this purpose could not be conveniently adjusted once the variation had been initially fixed and built into the carburetor. In the present invention unique means are provided which readily may be adjusted to suit specific conditions and requirements.

Referring again to FIGURE 2 in conjunction with FIGURE 1, the variation in the fuel passage is determined by a metering bar 52 disposed within housing 34 beneath the fuel pick-up arm 42. Metering bar 52 has an upper surface 53 which is broader than the fuel inlet opening 47 at the end of arm 42 and is curved to extend approximately along the circular arc described by the opening as the arm pivots about the throttle shaft 22, the bar being spaced slightly from the path of the opening to provide a fuel passage thereto.

A first end 54- of metering bar 52 extends a small distance beyond the closed throttle position of arm 42, indicated by dashed line 42 in FIGURE 2, and the opposite end 56 of the bar extends past the open throttle position of the arm which is indicated by dashed line 42". To fix the position of the bar 52 near end 56, a projection 57 is formed on the underside of the bar and extends a small distance downwardly, the surface of the projection facing end 54 of the bar being slidingly abutted against a shelf 58 formed at the corner of housing 34 so that the adjacent portion of the bar may be moved in the direction of the throttle shaft but may not move angularly therearound.

In order to provide the desired variation in the effective size of the fuel passage to pick-up arm opening 47, the bar is varying spaced from the end of arm 42 at the different positions thereof, the spacing being minimal near end 54, which corresponds to the idling setting of the carburetor, and being greater near end 56 which corresponds to the full power setting. Considering now the means by which the metering bar 52 is held in a desired position, in an adjustable manner, a full power adjustment screw 59 is transpierced through the wall of housing 34, adjacent shelf 58 and is threadably engaged in the projection 57 of the metering bar 52. Screw 59 has oppositely directed threads engaging the wall of the housing 34 and the bar projection 57 and a thick resilient washer 61 is disposed beneath the head of the screw at the exterior of the housing.

, Thus by rotating screw 59 the spacing of the metering bar 52 from the end of arm 42 may be adjusted for those positions of the arm in the vicinity of the full power position indicated by dashed line 42". Typically, screw 59 controls the setting between full power and about 80% thereof.

Another adjustment screw 62, which primarily provides for a summer-winter adjustment of the maximum spacing of arm 42 and bar 52 at idling position, is transpierced horizontally through the wall of housing 34 to bear against end 54 of the metering bar 52. Screw 62 is also threadably engaged with the wall of the housing and has a resilient washer 63 beneath the head thereof. As the bar 52 is formed of a resilient material such as spring steel, rotation of screw 62 acts to increase or decrease the spacing of end 54 of the bar from arm 42 in the vicinity of the lower power position 42' and thus limits the size of the fuel passage for idling and low speeds.

Adjustment of the fuel passage for intermediate or cruising speeds, typically from about 30% to 80% of full power, is primarily effected by still another screw 64. Screw 64, having a thick resilent washer 66 under the head thereof is transpierced horizontally through the wall of housing 34 to bear against the opposite end 56 of the bar 52, the screw being threadably engaged with the housing. Inasmuch as the bar 52 is held in fixed position at a nearby point by screw 59 and the opposite end of the bar is constrained from longitudinal movement by screw 62, the effect of rotating cruise adjustment screw 64 is to vary the curvature of the intermediate portions of the bar. The bar 52 pivots slightly about the region of projection 57 and thus the spacing of the central portion of the bar from the arm 42 may be adjusted.

To provide an automatic thermostatic adjustment of the idling setting, an additional screw 67 is transpierced through the corner of housing 34 near end 54 of bar 52 and directed towards the underside of the bar at a point corresponding to the idling position 42 of the arm 42, the screw being threadably engaged in the housing. Screw 67 has a longitudinal passage 68 in which a thermally sensitive rod 69 is disposed with the tip of the rod projecting from the screw to contact the underside of bar 52. Rod 69 is composed of a material having a very high coefficient of thermal expansion relative to that of the screw 67. Thus the screw 67 may be rotated, when the carburetor is cold, so that the tip of rod 69 just abuts the bar 52 and as the carburetor heats up the rod will ex and thereby urging the bar towards arm 42 and reducing the spacing therebetween as is desirable to maintain The change in the spacing of bar 52 from arm 42 required to effect the foregoing adjustments is generally very slight. It should be understood that the degree of spacing between the two members has been exaggerated in FIG- URES 1 and 2 for clarity of illustration and that for similar reasons the difference of such spacing between the low power and high power positions of the arm 42 is shown as abnormally large.

Considering now further components of the carburetor 11, and with reference to FIGURE 3, a deceleration vacuum relief valve 71 is disposed at the end of throttle shaft 22 within the housing 34. Valve 71 includes an internally threaded small cylindrical housing 72 having an inner end 73 of reduced diameter which extends axially into the end of the throttle shaft 22 and which has a passage 74 connecting with the throttle shaft fuel passage 48. A smaller cylinder 76 has a threaded inner end disposed coaxially in housing 72 in threaded engagement therewith and has an outer end which is closed except for a small central air aperture 77. A tapering valve seat 78 is formed inside cylinder 76 around aperture 77 and a ball 79 seats thereagainst to urge the ball 79 against seat 78, a compression spring 81 is disposed coaxially within cylinder 76 and housing 72.

Except during engine deceleration, the air aperture 77 is blocked by ball 79 and fuel is drawn through the passages 46 and 48 in the manner hereinbefore described When the engine is decelerating, an abnormally high vacuum is created in the carburetor and the resultant suction is sufficient to overcome the force of spring 81 and withdraw ball 79 from seat 78. This allows air, rather than fuel, to be drawn through passage 48 thereby suppressing the delivery of fuel of the venturi during deceleration. Adjustment of the opening timing of valve 71 is provided for in that turning the cylinder 76 will vary the force of spring 81 against ball 79.

Referring now to FIGURE 4 in conjunction with FIG- URE 1, the fioat chamber 36 includes a conventional fuel supply valve 82 projecting through an endwall thereof and coupled to a fuel supply conduit 83. Valve 82 is of the type having fuel outlets 84 within the housing 36 and having an actuating button 86. A rectangular float 87 is disposed within the housing 36 and is pivotably attached thereto, at the end nearest supply valve 82, by an arm 88 and pivot pin 89. A member 91 extends from the end of the float 87 to bear against supply valve button 86 and hold the valve closed when the float is in an elevated position. When the float 67 drops due to a lowering of the fuel level in chamber 36, member 91 retracts from the button 86 allowing the valve to open and restore the fuel level.

To prevent unrestrained movement of the float 87 which might result in damage and to damp excessive oscillation thereof, a coil spring 92 extends between the underside of the float and the base of chamber 36.

To provide for the injection of extra fuel into the venturi during engine acceleration, a pump 93 is disposed in the float housing 36, the pump being operated by movement of the throttle towards the open position. Referring now to FIGURE 5 in conjunction with FIGURE 4, pump 93 includes an inverted bell-shaped upper member 94 and an annular base member 96 disposed against the underside thereof, a flexible diaphragm 97 being disposed therebetween to close the upper member. Members 94 and 96 are supported a small distance above the base of housing 36 by four cylindical posts 98 having bolts 99 extending therethrough and securing member 96 to the housing.

Upper member 94 is provided with a small central fuel inlet aperture 101 which flares in the downward direction to form a valve seat for a ball 1612. Ball 102 is held adjacent the aperture 101 by a disc 103, having fuel passages 1fl4 therein, which seats against an annular shelf 106 formed around the undersurface of member 94 a small distance below the aperture. Inner and outer circular rigid discs 197 and 108 respectively are secured to the opposite sides of diaphragm 97 by a screw 109 and a compression spring 111 extends between discs 10?: and 107 to hold disc 103 in position and to urge the diaphragm downwardly.

Thus as the diaphragm 97 is urged downwardly by spring 111, ball 102 may retract from aperture 101 and fuel is drawn into the pump 93. An outlet 112 is provided in the wall of member 96 so that as the diaphragm 97 is forced upwardly by means to be hereinafter described, fuel is forced into the outlet. To deliver the fuel to the carburetor venturi, a tube 113, shown in FIGURE 4, leads to a passage 114 in the base of the housing which connects with a passage 116, shown in FIGURES 1 and 2 leading to a check valve 115 With an outlet at upper part of the venturi.

Considering now the mechanism for operating the pump 93, with reference to FIGURES 1 and 4 in conjunction, a lever 117 is pivotably attached to a raised pedestal 118 at the base of float housing 36 near the pump and has a first end 119 extending under the pump in position to bear against the underside of the diaphragm 97 thereof. The opposite end 121 of lever 117 extends upwardly between the float 87 and fuel pick-up arm 42. A pin 122 projects from collar 43 of arm 42 in position to bear against end 121 and pivot the lever 117 when the throttle shaft 22 turns towards the open throttle position. End 119 of the lever than bears upwardly against the underside of pump 93 to effect the pumping action hereinbefore described.

Referring now to FIGURES 6 and 7 in conjunction, a solenoid controlled valve 123 functions to provide additional fuel to the venturi when the carburetor is cold, as at starting for example, and includes control mechanism for operating the de-icer 19 and for providing a relatively high idling setting at low engine temperatures.

Valve 123 includes a cylindrical body 124 formed of non-magnetic material and disposed to project from a boss 126 on the carburetor barrel 12. A passage 127 extends through boss 126 from body 124 to the carburetor throat 13 with a tapered valve seat 128 being formed at an intermediate point in the passage. To supply fuel, an additional passage 129 extends from seat 128 through the wall of barrel 12 to an intake 131 (shown in FIGURE 2) in the fuel chamber housing 34. A valve member 132 is slidably disposed in passage 127 and is provided with a tapered point 133 adapted to seal in valve seat 128 to close the fuel supply passage 129.

Valve member 132 is operated by a cylindrical solenoid armature 134 which is slidably disposed in the valve body 124, the valve member being connected to armature 134 by a rod 136 which extends through the armature and projects a substantial distance from the end of the valve body. To hold the valve in a normally closed position, a compression spring 137 is disposed in valve body 124 to urge armature 134 in the direction of the valve seat 128.

To withdraw valve member 132 from seat 128 when the fuel mixture is to be enriched, a solenoid coil 138 is disposed coaxially around valve body 124 wherebyenergization of the coil acts to draw armature 134 into the coil against the action of spring 137. Coil 138 is enclosed by a housing 139 which provides space at one side of the coil for a thermostatic control 141.

Control 141 includes a bi-metallic element 142 having a stationary end secured to housing 139 and a free end disposed in proximity to One terminal 143 of the coil 138. The element 142 is of the type which deflects upon temperature changes and is positioned to contact the terminal 143 when at normal atmospheric temperatures but to deflect therefrom when heated to the higher temperatures characteristic of a carburetor on an operating engine.

The second terminal 144 of coil 138 is connected to a battery 146 through the previously described de-icer heating element 19 and a switch 147. The opposite side of battery 146 and the bi-metallic element 142 are grounded to complete the circuit. If appropriate, the battery 146 may be the customary storage battery of an automotive engine and the switch 147 may be the conventional ignition switch although separate components may be utilized if desired.

Thus when the switch 147 is closed and the carburetor is cold, current is supplied to coil 138 thereby causing arm re 134 to retract valve member 132 from seat 128.

Fuel supply passage 129 is thereby opened allowing the vacuum within throat 13 to draw extra fuel therethrough. Simultaneously the de-icer 19 is energized to heat the carburetor barrel and forestall icing difficulties.

When the carburetor has heated to normal operating temperatures the bi-metallic element 142 deflects from coil terminal 143 and opens the circuit. De-icer 19 is inactivated and spring 137 causes valve member 132 to seat and close the supplementary fuel passage 129.

If preferred, the enriching valve 123 and de-icer 19 may be separately controlled by manual means rather than by the automatic thermostat mechanism 141.

In starting a cold engine it is desirable to provide for a higher than normal idle setting of the throttle in addi tion to enriching the fuel mixture and forestalling icing. This is accomplished by utilizing the solenoid of enriching valve 123 to manipulate the previously described throttle stop 33. 1 s

In particular the stop 33 is comprised of an arm 148 pivotably mounted on boss 126 by a pin 149 and rotatable sleeve 151 thereon, a generally circular cam 152 being carried on the arm in coaxial relationship to the sleeve. The opposite end of arm 148 is coupled to the armature rod 136 which projects from the enriching valve 123, by means of an additional rod 153, and thus the cam 152 is turned when the valve opens or closes. The portion 154 of the cam 152 which is in the path of screw 32 when the enriching valve is closed has a radius which stops rotation of the throttle shaft 22 at the normal low idling setting and the portion 156 of the cam which is contacted by the screw when the valve 123 is open has a slightly greater radius to provide the high idling setting.

While the invention has been described with reference to a single exemplary embodiment, it will be apparent to those skilled in the art that many modifications and variations are possible within the scope of the invention and it is not intended to limit the invention except as defined in the following claims.

What is claimed is:

1. In a carburetor of the class in which fuel is transmitted to the barrel through a passage within the throttle shaft which extends thereinto, the combination comprising means defining a fuel chamber adjacent said barrel, an arm attached to said throttle shaft and having a free end extending into the fuel volume within said chamber, said arm being pivotable upon rotation of said throttle shaft and having a fuel passage connecting an axial opening at said free end of said arm with said fuel passage of said throttle shaft, and an adjustable curved metering bar disposed adjacent the curved path travelled by said opening of said arm as said arm pivots, means variably spacing and adjusting said bar from said opening at different positions of said arm to vary the effective size of the fuel passage therethrough at said different positions of said arm.

2. A carburetor as described in claim 1 wherein said metering bar is positioned by a plurality of threaded supports whereby the spacing of said bar from said opening of said arm may readily be adjusted.

3. A carburetor as described in claim 1 wherein said curved metering bar is formed of a resilient material and wherein means are provided for applying an adjustable compressive force to said bar to change the curvature thereof, thereby varying the spacing of at least portions of said bar from said path of said opening of said arm.

4. A carburetor as described in claim 1 and comprising the further combination of a thermally sensitive element of the class which expands upon being heated, said element being positioned to urge said bar towards said path of said opening as said carburetor heats up whereby the spacing between said bar and said opening is reduced at higher engine temperatures.

5. In a carburetor of the class in which fuel is delivered to the venturi throat through a passage in the throttle shaft extending thereacross, the combination comprising means forming a fuel chamber adjacent one end of said shaft, an arm secured to said shaft and having a free end extending into the fuel volume in said chamber, said arm being pivotable by rotation of said shaft and having a fuel passage connecting an opening at said free end of said arm with said passage of said shaft, a curved fuel metering bar disposed along the arc defined by said opening as said arm pivots, and a plurality of adjustable support elements extending through the wall of said fuel chamber'means at locations spaced along said bar for adjusting the spacing of said bar from said arc, said spacing being minimal at the first end of said bar which is adjacent said arm at the closed position of the throttle and progressively increasing towards the second end of said bar.

6. A carburetor as described in claim wherein said support elements are rotatable screws threadably engaged with said wall of said fuel chamber means and wherein a first and a second of said elements are positioned at said first and second ends respectively of said bar to exert oppositely directed forces thereon, and wherein a third and a fourth of said support elements are positioned at intermediate locations along said bar, said third element being relatively close to said first end of said bar and said fourth element being relatively close to said second end of said bar.

7. A carburetor as described in claim 6 wherein said fourth support element is attached to said bar to positively hold the associated portion of said bar in a selected position and wherein said first, second and third support elements are abutted against said bar.

8. A carburetor as described in claim 6 wherein said third support element is comprised of a member having a high thermal coefiicient of expansion, said member being abutted against said bar to raise said bar towards said opening as said carburetor heats up.

9. A carburetor comprising a barrel having a constricted portion defining a venturi throat, a float chamber housing adjacent said barrel for containing a fuel supply, a throttle shaft extending across said venturi throat to said float chamber, said throttle shaft having a fuel passage and at least one aperture within said venturi throat for emitting fuel into said throat, a throttle plate carried on said throttle shaft within said throat, an arm secured to said shaft within said float chamber housing and having a free end extending into said fuel therein, said arm being pivotable upon rotation of said throttle shaft and having a passage connecting an opening at said free end with said fuel passage of said shaft, a fuel metering bar disposed within said housing along the circular arc travelled by said free end of said arm as said throttle shaft is rotated, successive portions of said bar being increasingly spaced from the path of said opening to progressively increase the fuel passage size between the closed and fully open positions of said throttle plate, and means for selectively adjusting said spacing of said bar from said opening.

10. A carburetor as described in claim 9 wherein an air passage having a restriction therein connects to said fuel passage and comprising the further combination of a closure element disposed in said air passage and being seatable against said restriction to close said air passage,

and resilient means disposed in said air passage to urge said closure against said restriction whereby said air passage remains closed except upon occurrence of the very high degree of vacuum in the venturi which accompanies engine deceleration.

11. A carburetor as described in claim 9 and comprising the further combination of an acceleration fuel pump disposed in said float chamber housing and having an inlet communicating therewith and an outlet communicating with said venturi throat, said pump having an actuating means disposed in the path of said arm for operation thereby upon movement of said throttle plate from said closed position thereof towards said open position thereof.

12. In a carburetor of the class wherein fuel is delivered to the barrel through a throttle shaft which extends thereacross, the combination comprising means forming a fuel chamber adjacent the barrel, an arm attached to the throttle shaft and having a free end extending into the fuel volume within the chamber, said arm being pivotable upon rotation of the throttle shaft and having a first fuel passage connecting an opening at said free end of said arm with a second passage in said throttle shaft for delivery of fuel to said barrel, an adjustable curved meter ing bar disposed within said fuel chamber along the curved path travelled by said opening of said arm as said arm pivots, means variably spacing and adjusting said bar from said opening at different positions of said arm to vary the effective size of the fuel passage therethrough at said different positions of said arm, means forming a third fuel passage from said chamber to said barrel, and a mixture enriching valve controlling flow through said third passage, means opening said valve when said carburetor is relatively cold and closing said valve when said carburetor reaches normal operating temperatures.

13. A carburetor as described in claim 12 wherein said valve is operated by a solenoid coil and comprising the further combination of a thermostatic switch connected between said coil and a source of electrical current to control said coil, said switch being responsive to the temperature of said carburetor.

14. A carburetor as described in claim 13 and comprising the further combination of an electrically operated de-icing element disposed at said carburetor and connected to said source of current through said thermostatic switch whereby said element is energized as said valve is opened.

References Cited by the Examiner UNITED STATES PATENTS 2,094,555 9/ 1937 Von Hilverty.

2,190,314 2/1940 Firth 261-44 X 2,223,987 12/1940 Firth 261-44 X 2,236,595 4/1941 Fish 261-44 X 2,801,086 7/1957 Fish 261-44 X 2,895,723 7/1959 Weiland 261-44 3,017,166 1/1962 Sterner 3,128,321 4/1964 Hammerschmidt 261-44 X HARRY B, THORNTON, Primary Examiner. RONALD R. WEAVER, Examiner. 

1. IN A CARBURETOR OF THE CLASS IN WHICH FUEL IS TRANSMITTED TO THE BARREL THROUGH A PASSAGE WITHIN THE THROTTLE SHAFT WHICH EXTENDS THEREINTO, THE COMBUSTION COMPRISING MEANS DEFINING A FUEL CHAMBER ADJACENT SAID BARREL, AN ARM ATTACHED TO SAID THROTTLE SHAFT AND HAVING A FREE END EXTENDING INTO THE FUEL VOLUME WITHIN SAID CHAMBER, SAID ARM BEING PIVOTABLE UPON ROTATION OF SAID THROTTLE SHAFT AND HAVING A FUEL PASSAGE CONNECTING AN AXIAL OPENING AT SAID FREE END OF SAID ARM WITH SAID FUEL PASSAGE OF SAID THROTTLE SHAFT, AND AN ADJUSTABLE CURVED METERING BAR DISPOSED ADJACENT THE CURVED PATH TRAVELLED BY SAID OPENING OF SAID ARM AS SAID ARM PIVOTS, MEANS VARIABLY SPACING AND ADJUSTING SAID BAR FROM SAID OPENING AT DIFFERENT POSITIONS OF SAID ARM TO VARY THE EFFECTIVE SIZE OF THE FUEL PASSAGE THERETHROUGH AT SAID DIFFERENT POSITIONS OF SAID ARM. 